The most viscerally compelling argument for this that I know of in recent memory is the SR-71. You can go see one in the flesh here or there.
As the core applied sciences weaken and evaporate, everything else will stagnate. Modern CNC machines are indeed very impressive, but have you ever wondered why, to make things, we're still fundamentally shaving away metal?
If any given area of technology has advanced in the past 50 years, it's because it's become highly computerized, not because of breakthroughs in hardly any other area. Soon the reservoir of solid-state electronics will dry up, and we'll stagnate completely.
Once progress is halted entirely, things will start going backwards. Young people will look fondly upon the ruins of the once great civilization, and imagine the exciting hubbub of a society still breathing. Priuses will rust in great boneyards, stripped of ever simpler components. For a fanciful look at how society will appear then, try this or that. At least it will be more entertaining than the reality of what's to come.
Ah! The great march forward!